In a fuel cell stack having a large number of laminated fuel cells, it is important to distribute a fluid such as fuel gas evenly to each fuel cell in the stack and discharge the fluid evenly from each fuel cell. Each fuel cell is constituted by a cell main body and a separator laminated to either side of the cell main body. An in-cell fluid passage facing the cell main body is formed in the separator. Further, an internal manifold which distributes the fluid to the in-cell fluid passages and another internal manifold which collects the fluid that is discharged from the in-cell fluid passages penetrate in the fuel cell lamination direction, or in other words a direction that traverses the fuel cell stack longitudinally.
According to research conducted by the inventors, when fluid is supplied to an end portion of the internal manifold that opens to the outside of the fuel cell stack from an orthogonal direction, a large pressure deviation occurs in a transverse section of an upstream portion of the internal manifold. As a result of this pressure deviation, a bias occurs such that the fluid supply rate to the fluid passage of each fuel cell is low in the upstream portion of the internal manifold and high in a comparatively downstream part of the internal manifold.
Various proposals, such as the following, have been made with a view to correcting fluid distribution bias in a fuel cell stack.
JP2002-252021A, published by the Japan Patent Office in 2002, proposes disposing a columnar penetrating body at an appropriate gap from the inner periphery of the manifold and using this columnar penetrating body to rectify the fluid that flows into the manifold before supplying the fluid to the stack. JP2004-259637A, published by the Japan Patent Office in 2004, proposes connecting an introduction passage comprising a rectifying plate to the manifold. JPH06-314570A proposes rectifying the fluid by disposing a porous material between the manifold and the fluid passage.